He was a pupil of Santo Prunato and Antonio Balestra and active mostly in the area of the Veneto. He became the director of the academy of painting and sculpture of Verona in December 1764. The Academy was subsequently known as Accademia Cignaroli. Among his many pupils were Maria Suppioti Ceroni, Giovanni Battista Lorenzi, Saverio Dalla Rosa, Domenico Mondini, Domenico Pedarzoli, and Cristopher Unterberger. His brother Giovanni Domenico Cignaroli was also a painter.
For the Austrian governor of Lombardy and a collector of antiquities, Count Karl von Firmian, Cignaroli painted two canvases on Greco-Roman episodes, a thematic preferred by Neoclassic painters: Death of Cato (1759) and Death of Socrates.
Giambettino was born into a family of artists, and this tradition continued after his death with his children. Artists from his family who were contemporaries and elders of Giambettino include his uncle Leonardo Seniore, and his two sons (cousins of Giambettino), Martino and Pietro.
- Martyr of Saints Felix and Fortunatus (1737), Bergamo Cathedral
- Apollo and Marsyas (1739) and the Sacrifice of Iphigenia (1741), Villa Pompei, Illasi, Verona
- Saint Helena (1741), Castelvecchio, Verona
- Saint Procolus Visiting Saints Fermus and Rusticus (1744), Bergamo Cathedral
- Virgin and Child With Saints Jerome and Alexander (1744), Chiesa dell'Ospedale, Bergamo
- Aurora (1748), Casa Fattori, Verona
- Death of Rachel, Accademia, Venice
- Death of Socrates (1759)
- Death of Cato (1759)
- Sacrifice of Isaac
- The Travels of Moses
- Web Gallery of Art
- Giambettino Cignaroli's Deaths of Cato and of Socrates, Joseph Geiger. Zeitschrift für Kunstgeschichte (1996) pp270–278.
- Studi sopra la storia della pittura italiana dei secoli xiv e xv e della scuola pittorica. By Cesare Bernasconi. Published 1864 (google books). Original from Oxford University
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